1. Technical Field
The present invention generally relates to a semiconductor memory device, and more particularly, to a nonvolatile memory device, an operating method thereof, and a data storage device having the same.
2. Related Art
In general, a semiconductor memory device is classified into a volatile memory device and a nonvolatile memory device. The volatile memory device loses data stored therein when power supply is cut off, but the nonvolatile memory device maintains data stored therein even though power supply is cut off. The nonvolatile memory device may include various types of memory cells.
The nonvolatile memory device may be divided into a flash memory device, a ferroelectric RAM (FRAM) using a ferroelectric capacitor, a magnetic RAM (MRAM) using a tunneling magneto-resistive (TMR) layer, a phase change memory device using chalcogenide alloys and the like, depending on the structure of memory cells.
Among the nonvolatile memory devices, the flash memory device is roughly divided into a NOR flash memory device and a NAND flash memory device, depending on the connection state between memory cells and a bit line. The NOR flash memory device has a structure in which two or more memory cell transistors are connected in parallel to one bit line. Therefore, the NOR flash memory device has an excellent random access time characteristic. On the other hand, the NAND flash memory device has a structure in which two or more memory cell transistors are connected in series to one bit line. Such a structure is referred to as a cell string, and one bit line contact is required per one cell string. Therefore, the NAND flash memory device has an excellent characteristic in terms of integration degree.
The nonvolatile memory device may perform a program operation through a plurality of operation loops. Such a program loop includes a program voltage application operation of applying a program voltage to a selected memory cell and a program verify operation of verifying whether or not the selected memory cell is programmed to have a desired threshold voltage. When it is determined through the program verify operation that the program operation is passed, the program operation is normally completed. However, when it is determined through the program verify operation that the program operation is failed, the program loop is repetitively performed until the program operation for the selected memory cell is passed. Whenever the program operation loop is repeated, the program voltage applied to the selected memory cell increases.